The thickness of silicon substrates used in solar cell modules is gradually decreasing in order to reduce the manufacturing cost and the silicon substrates that are currently used have a thickness of equal to or less than 0.2 mm.
On the light receiving surface of a silicon substrate, a diffusion layer is formed, and an anti-reflective film and a silver electrode are formed sequentially thereon. On the non-light receiving surface, an aluminum electrode and a silver electrode are formed, thereby forming a solar cell having a power generation function. Solar cells are electrically connected in series with each other by solder-dipped flat rectangular copper wires, thereby forming a solar cell string or an array.
The light receiving surface side of the solar cell array is covered with a front surface material with a sealing resin therebetween and the non-light receiving surface side is covered with a back surface material with a sealing resin therebetween. The members are integrally molded by heat-sealing the sealing resins in a vacuum.
Typically, ethylene-vinyl acetate (EVA) is used for the sealing resin, glass is used for the front surface material, and a laminated sheet of a PET (polyethylene terephthalate) film or a fluorine film is used for the back surface material.
For a lamination process in which the above integral molding is performed, a laminating apparatus including a vacuum heating and pressurizing mechanism is used. The details of the lamination process will be explained next.
A laminate, in which a front surface material, a sealing resin, a solar cell array, a sealing resin, and a back surface material are superimposed in sequential order starting from the light receiving surface side, is set in the laminating apparatus. The laminate is heated by a heater in the laminating apparatus, in which air is evacuated. In a state where the sealing resins are heated to around their melting points, pressure is applied to the laminate. In this state, the sealing resins are further heated to around 150° C., which is maintained for a predetermined period of time, therefore, the sealing resins are cross-linked and the laminate is integrally molded.
For the above technology, the technology (for example, see Patent Literature 1) in which a sealing resin layer is used for each of the light receiving surface and the non-light receiving surface and the structure of a laminating apparatus (for example, see Patent Literature 2) are already disclosed.